SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '2b721f0ace4f3a9c355e7435293fba74e6688cfe7dda35c942bfecc6b67a7fc7' 
  AND token = 'pj4P1RvjS7iH8Ki8rwzpvGQZpEDB1qZyp7/VS6SSsTE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}